This invention relates to apparatus for removing material from a workpiece with a tool and, more particularly, to apparatus for changing the rake angle of a given tool.
In the mechanical processing of materials, the shape, size or properties of a given workpiece are altered. Those processes in which the size and shape are changed by removing material with a tool are classified as metal cutting. In practice, all operations such as turning, boring, drilling, milling, reaming, tapping, and cutting fall into this single category of metal cutting.
In a metal cutting process, an important parameter governing the cutting conditions, such as cutting force, is known as rake angle. This angle, which will be described in detail below, is determined in part by a face on the tool known as the rake face. Usually, tools with different rake faces are selected for different cutting conditions so that, for example, one rake angle is used for machining a brass workpiece and a different rake angle is used for machining steel.
In current practice, a tool or cutting member having a particular rake face is fixed on a tool holder whereby the tool rake angle is fixed and cannot be changed. If, for example, workpieces of different materials are to be machined, either different tools having different rake faces should be used for the machining operation, or a given tool have its rake face reground. This, of course, is disadvantageous in that there is required a number of different tools for machining workpieces of different material, or additional time and expense is needed in regrinding a given tool to machine the different materials.
Moreover, the deflection of a workpiece is related to cutting force. That is, during the machining of a workpiece in, for example, a lathe operation, a constant cutting force on a cylindrical workpiece may cause varying degrees of deflection of the workpiece, with a greater deflection occurring at the central portion of the workpiece where it is unsupported and a lesser deflection at the end of the workpiece where it is supported. This can undesirably result in dimensional non-uniformity of the cut workpiece. Since a change in rake angle can change the cutting forces, it is desirable to improve dimensional uniformity by changing the rake angle in-process, i.e., while the workpiece is being cut.